Stir together the jam and 4 tablespoons of the Grand Marnier in a small bowl to blend.

Stir together the mascarpone and remaining 2 tablespoons of the Grand Marnier in a large bowl to blend. Using an electric mixer, beat the cream, granulated sugar, and vanilla in another large bowl until soft peaks form. Using a large rubber spatula, stir a fourth of the whipped cream into the mascarpone mixture to lighten. Fold the remaining whipped cream in to the mascarpone mixture.

Line the bottom of a 13- x 9- x 2-inch baking dish or other decorative serving dish with a third of the ladyfingers. Spread a third of the jam mixture over the ladyfingers. Spread a third of the mascarpone mixture over the jam mixture, then cover with a third of the fresh raspberries. Repeat layering with the remaining ladyfingers, jam mixture, mascarpone mixture, and raspberries. Cover and refrigerate at least 3 hours or overnight.